In any city, light rail transit (LRT) has the potential to significantly
increase the capacity of the public streets and roadways in which
it operates. This is often not grasped by opponents and critics
who resist reallocating traffic lane capacity, from being exclusively
dedicated to motor vehicles, to either sharing the space with LRT
or dedicating it exclusively to LRT. These opponents often
include highway engineers, public works officials, local politicians,
and, indeed, many ordinary motorists.

But cities cannot keep "chasing" the rise in motor vehicle traffic
with fruitless efforts to maintain roadway capacity. Traffic
volumes – dependent mainly on private automobiles – are far
outstripping street and road capacity, and the ability and
resources of urban governments to provide that capacity.

Even the lowest level of LRT – streetcars
(tramways), such as the Philadelphia city system pictured at right – offers major advantages in people-moving capacity.
Streetcars or trams can be found throughout European and Japanese cities.
in North America, cities like Toronto, Boston, Philadelphia, Pittsburgh, New Orleans, and San
Francisco have retained portions of their original street railway
systems; Portland has installed a brand-new, modern streetcar
system; and Tacoma is doing the same. New Orleans and
Portland have embarked on an ambitious and unique program of
streetcar system expansion, and Boston also has a streetcar expansion project under way.

It's essential for every citizen to understand that, while streetcars
(or other forms of LRT) may "get in the way" of automobiles, they
vastly increase the capacity of the street to move people – even
when sharing the roadway lanes with mixed traffic. Most
motorists do not realize that.

Portland streetcar increases city streets' people-moving capability.

If we add a rail line to the center of the street, it may cut the
carrying capacity of the street lane from 900 passengers per hour
by auto to 750 as rail cars "hamper" auto movement. But if the
rail line is justified (in terms of ridership, cost-effectiveness, net
benefits, etc.), it may be moving 1,500, 2,500, or even more than
4,000 people per lane per peak hour. And keep in mind that
streetcars can be operated in trains – typically, two to three cars in length.

Buses, of course, could be used instead, but they will consume
more auto space and, almost surely, move fewer transit riders.
instead of 750 passengers remaining in automobiles per lane, the
passenger flow will drop to 600 as more buses than rail cars are
needed. Furthermore, buses, on average, will attract
approximately thirty percent fewer riders than LRT because of the
comparatively lower passenger-attraction characteristics of buses
(see Transportation Research Board Report 1221). Thus, only
1,050, 1,750, or perhaps 2,800 passengers will be moved per lane
per peak hour. LRT is far more likely to make the best and most
efficient use of the street lane for the public at large.

These characteristics are summarized in the following table:

Peak Passenger Capacity per Lane per Hour

Traffic Level

Auto Only

Auto + Bus

Auto +
Streetcar

Low Volume

900

1,650

2,250

Medium Volume

900

2,350

3,250

High Volume

900

3,400

4,600

Certainly, any form of LRT will work better if it is not mixed with
automobiles. But if there is no other route to follow, street or road
lanes can and should be used. After all, virtually all cities have
ubiquitous traffic, economic, safety, and pollution problems that
need to be solved. Substantially increasing passenger-flow
capacity through the introduction of attractive streetcar-type LRT
can contribute to the solution.